Composite filament



Jan. 14, 1964 A. L.-BREEN COMPOSITE FILAMENT Fil ed June 20. 1961 3Sheets-Sheet 1 FIG.2

INVENTOR AlV/IV ZEMIRD BREE/V ATTORNEY A. L. BREEN COMPOSITE FILAMENTJan. 14, 1964 3 Sheets-Sheet 3 Filed June 20, 1961 FIGJZ INVENTOR AZVl/V [[OMRD Bflff/V United States Patent F 3,117,362 COMPOSITE FILAMENTAlvin Leonard Breen, Wilmington, Del., assignorto E. I. du Pont deNemonrs and Company, Wilmington, Del.,

a corporation of Delaware Filed June 20, 1961, Ser. No. 118,470 19(Ilaims. (Cl. 57140) This invention relates to improved synthetictextile filaments and yarns and a process for their production.

This application is a continuation-in-part of my copending applicationsSerial No. 412,871, filed February 26, 1954, now abandoned, Serial No.738,166, filed May 27, 1958, now abandoned, and Serial No. 754,064,filed August 8, 1958, now abandoned.

Filaments consisting of two or more components are known in the art.Such filaments are produced by extruding the different components fromthe spinneret in sideby-side relationship or in an eccentricallydisposed sheathcore arrangement. The components usually are so selectedthat they have different shrinkage characteristics when the filament isheated in a relaxed state with the result that a crimped fiber can beproduced. Yarns composed of these crimped or crimpable filaments havebeen found useful in producing yarns and fabrics having certain desiredproperties and aesthetic qualities. However, in the field of syntheticfibers produced from polymers such as the polyamides and polyesters ithas not been possible to achieve the desired level of such propertiesand aesthetic appeal except in limited areas. Further improvements inthe properties and aesthetics are very desirable. Particularly, a yarnof synthetic fibers having the aesthetic appeal and properties of silkfibers would be highly desirable in view of the other excellentfunctional characteristics of these synthetic fibers.

Much effort has been expended towards the preparation of yarns andfabrics that are silk-like from filaments of modern synthetic polymers.Although various proposed methods have duplicated one or more of theimportant characteristics of a silk fabric, a completely satisfactorysubstitute has not yet been found.

The desirability of producing textile filaments having one or more sharplongitudinal edges in order to produce silk-like yarns has long beenrecognized. Despite numerous proposals mainly drawn to extrusion orificedesigns, it has not been feasible to produce textile filaments havingsufficiently well defined sharp edges in cross-section by the extrusionof melts or solutions of fiber-forming polymers. This is due to the factthat the surface of a filament formed by extrusion through an orificerapidly tends to assume the transverse cross-sectional contour of acircle, the smallest boundary for the given cross-sectional area.

It is accordingly one object of this invention to provide a synthetictextile filament which may be used to produce yarns and fabrics ofgreatly enhanced aesthetic appeal and improved properties.

Another object is to provide a synthetic textile filament which may beused to produce yarns and fabrics similar to silk in aesthetic quality.

A further object is to provide a process for the produc tion of thesefilaments.

Other objects and advantages will become apparent from the examples anddiscussion to follow.

The above objects are accomplished by the provision of a compositefilament comprising a first longitudinally extending component of onesynthetic polymeric composition, and an adhering second distinctlongitudinally extending component of another synthetic polymericcomposition, said components closely fitted together along at least onecontacting surface to form the composite filament, said contactingsurface forming at least one longitudinally extending, sharp-edgeconfiguration, said com- 3,117,362 Patented Jan. 14, 1954 "ice ponentshaving different shrinkage potentials when subject to heat and undercertain conditions being readily separable along said contacting surfaceinto separate filaments, at least one of which is provided with alongitudinally extending sharp-edge configuration. Preferably, in orderto cause component separation to occur as desired, the average adhesionforce between the contacting surfaces of the dry components iscontrolled and is in the range of about 13.0 g./cm. up to the force todraw the material of the weaker component. The component, which has thehigher shrinkage has the higher denier.

In the accompanying drawings,

FIGURE 1 is an axial cross-section of a spinneret assembly used toprepare filaments of the present invention,

FIGURE 2 is a reduced transverse cross-sectional view of the assembly ofFIGURE 1 taken at line 22 of FIG- URE 1,

FIGURE 3 is a reduced transverse cross-sectional view of the FIGURE 1assembly taken at line 33 of that figure,

FIGURE 4 through 7, 9, 10 and 13 are transverse crosssectional views ofexamples of various filaments embodying the present invention,

FIGURE 8 is a transverse cross-sectional view of a single componentelement formed by the separation of a composite filament,

FIGURE 11 is an axial section of a modified version of a spinneretassembly used to prepare filaments of the invention,

FIGURE 12 is a transverse cross-sectional view of the assembly of FIGURE11 taken at line l2-12, and

FIGURE 14 is an axial cross-sectional view of another version of aspinneret assembly used to prepare filaments of this invention.

The composite filaments of my invention, may be stretched and theresultant drawn filaments subjected to a shrinking treatment to producefilaments having a large number of crimps per unit length. The crimp inthe filaments of this invention is brought about by a difference inshrinkage of the two components in the after treatment. The polyestercomponent in a polyester-polyamide composite filament, when the drawncomposite filament is subjected to shrinkage treatment, contracts to agreater extent than the polyamide component if the filaments have beencold drawn. This results in a distinct permanent helical crimp wherebythe inner portions of the cross sections in the single coils are formedby the polyester. If the filaments are length stabilized as disclosed inmy U.S. Patent 2,931,091, shrinkage treatment at moderate temperatures,i.e., about C., would result in the polyamide shrinking to a greaterextent than the polyester component and becoming the load-bearingcomponent. However, at higher temperatures the shrinkage of thepolyester component becomes greater so that the polyester componentbecomes the load-bearing element.

Although the crimped filaments described above may be used to produceyarns and fabrics of somewhat improved aesthetics, it is desirable thatthe filaments also are treated to separate the filament components. Thisresults in the creation of filaments of significantly reduced denier andthe separation is accomplished so that the low denier filaments producedhave sharp edges, which in combination with the bulking effect due todifferential shrinkage of the components results in novel improvedsilk-like yarns having a high level of aesthetic appeal and excellentfunctional qualities. In general and preferably, the polymers adherewell throughout processing of the side-by-side structures prior to thecomponent separating step. The strength of the bonding between thecomponents of the composite filaments depends to some extent on theparticular polymers of the components. In the production of thesestructures, for instance from polyamide, polyester combinations, it hasbeen found possible to separate or pull apart the components to producefilaments, either substantially polyamide or substantially polyester,which have very sharp boundary lines or surfaces. The shape of suchstructures depends on the location of the boundary between the twopolymers and the compos ite and the shapes may be, for example, crescentor oval. Thus, while the components adhere well during the initial stepsof drawing and winding of the yarn, they may be readily split apart bysuitable treatment of the yarn, such as drawing under tension over asharp edge with a significant change in direction of movement.

In accordance with one embodiment of the invention a composite filamenthaving a substantially uniformly shaped transverse cross section alongits length is composed of segments of at least two dissimilar syntheticpolymeric compositions. This cross section is provided with at least twosegments of at least one of said polymers, any contact between suchsegments of the same polymer being substantially point contact asextruded. This may be accomplished through the use of a spinneretassembly as more completely described below. After drawing as desired,the filament may be separated into its compo nent sections by thedesired action. Alternatively, all sections composed of one polymercomposition are separated or removed as for example, by dissolution orchemical decomposition.

By the term segment is meant a portion of a filamentary transversecross-section having at least one sharp point formed by theintersection, at a small acute angle, of two straight or curved lines,which are the boundaries of different polymer components. The segmentmay have: one sharp point such as in a tear-drop-shape as shown in 110of FIGURE 9; two sharp points such as in a lensshape as shown in 103 ofFIGURE 5, or such as in the shape shown in 1&7 of FIGURE 7; three sharppoints as in a plane triangle illustrated by segments 112 and 113 ofFIGURE 10 or curvilinear triangle as shown in FIG. 8; or a multiplicityof sharp points such as in a figure formed by the joining of 2 or moresimple segments as in a forme cross.

FIGURE 1 shows in axial section a spinneret assembly useful for thispurpose. Front or bottom plate I with orifices 2 is recessed at the backabout plateau-like protrusions 4. Back or top plate 7 is' sealed againstand spaced from the front plate by gasket 6 and shim l6. Relativelyunconstricted region 12 between the two plates is interrupted atintervals by constricted regions 15 between the opposing face of theback plate and plateaus 5 of the protrusions from the front plate. Theback plate is partitioned on top by outer wall 19. and inner wall 29into annular chamber 3 and central chamber 9. The annular chambercommunicates with the constricted regions between the two plates throughlead holes 31 and orifices 32, and the central chamber communicates withthe intervening relatively unconstricted region through holes 21. Thetwo plates are retained in place by cap 18 which is threaded onto theend of the back plate and is fixed to the front plate with set screws17. The upper part of the housing (not shown) receives suitable pipingor other supply means for separate connection to the two chambers, whichmay constitute distribution or filtering spaces as desired. Pin 14through cylindrical openings (opening in the front plate and opening 26in the back plate) near one edge of the plates ensures rotationalposition ng of the two plates.

FIGURE 2 shows a reduced view of the plan of the front plate. Appearingin this View are four plateaus,

each conwntric with an ex rusion orifice and uniformly spaced about acircle inside the outer gasket. As shown in this view and in FIGURE 1,each orifice consists of opposing face of the back plate being similarlygrooved to ensure a good seal between the two plates. FIGURE 3 shows areduced view of the back plate sectioned as indicated on FIGURE 1.Visible are the concentric outer and inner walls, the capillaries andcounterbores of four apertures spaced uniformly on a circle between thetwo walls, and four openings located within the central chamber definedby the inner wall. As shown in this view, the apertures in the top orback plate opposite the orifices of the bottom plate are each composedof four terminal capillaries 32 and introductory counterbore or leadhole 31.

Operation of the described apparatus in the practice of this inventionis readily understood. Di ferent polymer compositions are supplied tothe inner and the outer chambers, respectively, of the back plate; theformer flows through the openings into the relatively unconstrictedspace between back and front plates, through the relatively constrictedregions between the plateaus and the opposing plate face, and throughthe extrusion orifices while the latter passes first through theapertures in the back plate and directly onto the top of the plateau andthen through the aligned orifices in the front plate.

In the preparation of side-by-side structures a spinneret such as thatshown by FIGURES 11 and 12 also may be used. The spi-nneret shown iscomposed of two parts. In the upper portion 216 are two chambers 217 and218 cooperating with holes 219 in the bottom plate of the top portion.These holes permit the feeding or" polymer to grooves or recesses 22s inthe bottom portion 221 of the spinneret. The polymer coming from hole219 goes into the recess 222 immediately below it and is fed to aplurality of recesses 22%. Each recess contains and co operates with aspinneret hole 224. In each spinnerct, provision is made for a gasket2.25 and conventional means, as by bolting or pressure, can be used tohold the various spinneret elements in place during operation.

In this arrangement polymer coming from chamber 23.7 and the otherpolymer coming from chamber 218 meet at the orifices 224 and areextruded simultaneously to form side-by-side structures. Cross sectionsof such structures are indicated in FIGURE 13 by reference numeral Aspinneret of the type shown in FIGURE 14, in which two polymericcompositions are fed through converging channels to spinneret orificesare located in bottom plate 331 may be used to form the filaments ofthis invention. The two polymeric compositions are fed separately fromannular channels 333 and 334, respectively, which are positioned in topplate 332, into channel months 335 and 336, respectively. The polymerstreams are advanced through the channels to positions 337 and 338 andare then simultaneously extruded through the orifices to formside-by-side structures.

The following examples are given to illustrate applicants invention andare not to be considered as limiting in any sense.

EXAMPLE I Side-by-sidc composite crimped filaments were produced fromthe polytt'hexarnethylene adipamide) and poly(ethyl ene terephthalate).The polymers were melted separately and the melts were led separately tothe holes of the spinneret similar to that described by FIGURES 11 and12, with the exception that instead of a grouping of five channels-fiveorifices as shown in FIGURE 12 a grouping of four channels-four orificeswas used with the orifices being all close to the center line ratherthan being staggered as shown in FIGURE 12. The filaments wereattenuated by winding them up at about times the speed with which theyleave the spinneret. They were then cooled by a transverse stream ofair. The composite filaments thus obtained were drawn over two sets ofcold rolls whereby the second pair was driven at a circumferential speedbeing 3.0 times as high as of the first pair. When the drawn filamentswere placed in boiling water, the filaments crimped spontaneously. Thecrimped filaments had, on an average, 80 crimps per inch and a crimppermanence of 95%.

Sometimes it might be desirable to spin through one spinneret a bundleof filaments which comprises composite filaments containing thecomponents in various ratios. Such a bundle of two-component compositefilaments may comprise, for example, filaments consisting of 20% yweight of the polyamide and 80% by weight of the polyester, 30% of thepolyamide and 70% of the polyester, 40% of the polyamide and 60% of thepolyester, and 50% of the polyamide and 50% of the polyester. Suchfilament bundles containing composite filaments with various ratios ofcomponents have, after crimping, unique properties and have specialapplications, especially in the field of producing worsted fabrics fromcontinuous crimped filaments. They can very conveniently be produced byutilizing the spinneret which is shown by FIGURES 11 and 12. In FIGURE12 it will be noted that the orifices 224 are staggered. The pressure onthe melts in the first instance is the same, but where the paths fromchamber 217 and from chamber 218 to a given spinneret differ in length adifference in pressure on the respective polymers at the orifices willoccur because the diiference in pressure drops. Thus, at those orificesnearest the feed side supplied by chamber 217 a filament will beextruded which contains more of the polymer coming from chamber 217 thanof the polymer coming from chamber 218. Conversely, more polymer comingfrom chamber 218 will appear in filaments coming from orifices locatednear chamber 218, these filaments having less of the polymer coming fromchamber 217. These filament bundles obtained contain the polyamide andthe polyester in the various ratios. After drawing these filaments asdescribed, and placing them in the boiling water, a yarn of crimpedcontinuous filaments is obtained which has desirable properties due tothe fact that the single composite filaments in the bundle show varyingdegrees of crimp tightness and extensibility.

These filaments varied in polyamide/polyester amounts some being in20/80, 40/60, 50/50, 30/70 ratios, respectively, for example. Typicalcross-sections of such filaments are shown in FIGURE 13 wherein 227designates polyamide and 228 designates polyester.

EXAMPLE II Side-by-side composite filaments were prepared frompoly(hexamethyl ne adipamide) having a relative viscosity of 40 incresol and poly(ethylene terephthalate) having a relative viscosity of29 in a solution of trichlorophenol (7 parts) and phenol parts)following the general procedure of Example I. A spinneret of the typeshown in FIGURE 14 was employed. The two polymers were fed to thespinneret holes 340 in ratio by weight of 37% polyamide and 63%polyester. The composite filaments had trilobal cross-section of thetype disclosed in US. Patent 2,939,201. The filaments are attenuated byWinding them up at about 500 times the speed at which they leave thespinneret. The filaments were air quenched and drawn to a ratio 3.7 overa 90 C. pin and wound into a package in the conventional manner. Thefinal drawn yarn consisted of 26 filaments of 2.7 denier each, thepolyamide component being 1.0 denier and the polyester component 1.7denier. When the yarn is placed in hot water in a relaxed state withoutagitation, the filaments crimp. The filaments, in fabric form, weresplit apart by suitable mechanical action and heat set at 400 F. Afabric made of such separated-component filaments was characterized by awarm, soft hand, good resilience, a non-synthetic subdued luster, highbulk, high cover and excellent uniformity of dyeing despite being madeof polymers of different dyeing characteristics. In addition, the fabrichighly resembled silk in aesthetics. The cohesion between the polyesterand polyamide components in the filaments can conveniently be determinedby cutting about 8 cm. lengths of the filaments, splitting thecomponents apart at one end by flexing the end, or if necessary byimmersing the end in a swelling agent for one of the components, e.g., a5% aqueous formic acid solution, attaching one of the split apartcomponents to a sensitive strain gage and the other component end to arod which is drawn away from the strain gage at a constant rate of 2.4cm./ min. The force required to pull the components apart is recorded byan electronic recorder attached to the strain gage. The strain gageemployed was a Statham Instrument Company gage having a range of 550.15oz. The signal from the gage was fed to a preamplifier, then to anamplifier and finally to a conventional Sanborn recorder. The rod towhich one of the component ends was attached was floated in a horizontalposition in a container of water by means of two corks. A filament orstrand of yarn was attached to one end of the rod and the other end ofthe yarn passed around a small motor driven roller to drawn the rod awayfrom the strain gage at a slow, constant rate of 2.4 cm./min. Tocompensate for differences in denier and cross-sectional shape, thelength L of the interface between the adhered components of thecomposite filament is determined and the measured force, F, divided bythis value. This length L is measured on a photomicrograph taken at highmagnification of a transverse cross section of the composite filament byrolling a map reader along the clearly visible line at the interface ofthe different components.

Since the measured force varies as the composite filament is splitapart, the percentages of the filament length which split within givenranges of force are multiplied by the mean force for each range and thesum of these values divided by to obtain the average force required tosplit the filament. In carrying out this operation the ranges shown inthe following table were employed. The values shown in the first columnin the following table for percent splitting are averages of valuesobtained on 17 filaments. Likewise, the interface length L used in thecalculation was the average for the same 17 filaments. The values ofTables I and II correspond to filaments of a highly satisfactory natureand performance according to this invention, whereas the values of TableIII correspond to filaments approaching unsatisfactory nature andperformance.

Table I Percent Range, Mean, Percent Avg, Split gJcm. gJcm. SplitXg./cn1.

Means Table 11 Percent Range, Mean, Percent Avg Split gJcm. g./cm.SplitX gJcm.

Means An average cohesion value of at least about 13 -g./cm.

- was determined to characterize satisfactory samples of preferred yarnstested. These values were determined in the manner described above.

The fabric made from the yarn was judged to be more silk-like inaesthetics than any synthetic fabric available, including fabrics withtrilobal filament cross-sections and mixed shrinkage, filaments. Thefabric had a combination of a warm, soft hand; good resilience and anonsynthetic, subdued luster. In addition the fabric had high bulk andcover and excellent uniformity of dyeing in spite of the fact that itwas made up of polymers which dyed differently.

The fabric was subjected to 15 Wash cycles along with nylon and Du PontDacron polyester fiber controls and evaluated after each fifth Wash. Thefabric made from the filaments of this invention was found to besuperior to nylon in launderability and about equivalent to 100% Dacronfabrics which are well known for their excellent performance.

EXAMPLE III Example II was repeated except that the composite filamentswere of 4 denier each, the poly ethylene terephthalate) andpoly(hexarnethylene adipamide) components each being 2 denier. Thefabric made from this yarn had good bulk and cover but lacked thewarmth, softness, and luxurious handle exhibited by the fabric ofExample II.

EXAMPLE IV A spinneret similar to that shown in FIGURES 1 to 3 with 17orifices was constructed. The plateau 4 'was /is inch in diameter and Ainch high. The counterbore '22 was 40 mils in diameter and extended towithin 48 mils of the face of the spinneret. The capillary 21 had adiameter of 12 mils. The lead hole 31 in the upper plate 7 was inch indiameter and was drilled to within 94 mils of the bottom of plate 7. Theupper orifices 32 were 9 mils in diameter and were drilled on a circlehaving a. 39.5 mil radius the center of which was concentric with theupper lead hole and with the plateau in the orifice in the lower plate.The spinneret was assembled with a 3 mil thick shim l6.

Poly(hexamethylene adipamide) of 1 (relative viscosity) 36 in 90% formicacid at 25 C. was fed to chamher 9 of the spinneret and extruded to formthe triangular segments of the filament and poiy(ethylene terephthalate)of i 33 in a 7/10 mixture of tetrachlorcphenol/phenol at 30 C. andcontaining 0.3% of TiO was fed to annulus 8 and then through orifices 32to form the forme cross segment of the filaments cross-section. The twomolten polymers were extruded in the ratio of 9.5/ 10.0 by volumerespectively at 290 C. and the yan wound up at 1,000 y.p.rn. The yarnwas drawn 4X over an 88 C. pin and then passed over a 140 plate toreduce shrinkage. A cross-section of a typical filament is shown in=FZGURE 7. The yarn had a tenacity of 3.9 g.p.d., an Mi (initialmodulus) of 53, an ultimate elongation of 32% and a total denier of 50.

The yarn was knitted into a tubing which was quite lean 8. in appearanceand had poor visual covering power. The tubing was extracted for 3 hourswith 98% formic acid in a Soxhlet extractor, removed, rinsed with waterand dried. Despite the loss of about 50% of the fiber weight bydissolution of the polyarnide sectors the visual covering power of thetubing was greatly increased. The extracted tubing had a soft silk-likehandle and was scroopy. The cross-section of filaments remaining in theextracted fabric resembled a forme cross as shown in 100 of FIG- URE 7.

EXAMPLE V Using the same spinneret as in Example IV, poly(ethyleneterephthalate) of 1 26.9 in a 7/ 10 mixture of tetrachlorophenol/phenolat 30 C. and containing 0.3% of TiO was fed to chamber 8 of thespinneret and extruded as the segments of a composite filamentdesignated 101 in FZGURE 4 while poly(hexamethylene adiparnide) of 1: 36in 90% formic acid at 25 C. was fed to chamber 9 and extruded as thesegments of a composite filament designated 1.02 in FIGURE 4. Thepolymers were extruded at 290 C. and the yarn wound up at 400 y.p.n1.The yarn was drawn 4.3 X over a 98. C. pin. The resulting yarn had atenacity of 4.1 grams per denier, an initial modulus of 56 and had adenier per filament of 8.3. A portion of the drawn yarn was Wound on aperforated metal bobbin and immersed in cold 98% formic acid for 3hours. After rinsing and drying the residual polyester yarn bad atenacity of 3.8 g.p.d., a Mi of 73, an ultimate elongation of 28% and atotal denier of 80 for the 68 filaments then present. A typicalcross-section of a filament is shown in FIGURE 8.

A portion of the original yarn was woven into a 2 x 2 twill fabrichaving yarns per inch in the warp and 84 yarns per inch in the filling.The resulting fabric was immersed in 98% formic acid for 60 minutesuntil the poly(hexamethylene adipamide) sectors were dissolved from thecomposite filaments. The fabric possessed all of the properties of asilk fabric as liveliness and drape, the subtle scroop of silk, thehandle, the low denier per filament, the high modulus and good recoveryproperties.

A repetition of the above spin with positions of the two polymerschanged gives filaments which after treatment with formic acid leavesfillet-shaped sectors of the polyester similar to segment 102 of FIGURE4.

EXAMPLE V1 The following example illustrates the different crosssectionsobtained by varying the volume of polymers delivered to various sectorsof the composite filaments.

were extruded at 290 C. and the yarn wound up at i 1,000 y.p.-rn. Thevolume of the two polymers entering the composite filaments were variedby adjustment of their respective constant displacement pumps. In thefirst spin the volumes of the pigmented polymer to the non-pigmentpolymer was 1:1 and filaments were obtained having cross-sectionssimilar to that shown in FIG- URE 4. When the ratio of pigmented tobright polymer was set at 4/16, filaments with cross-sections similar toElGU-RE S were obtained. When the pumps were adjusted to give a ratio of16/4 as above cross-sections similar to FIGURE 6 were obtained.

above spins are repeated replacing the unpig merited polyester with thecopolyester poly[ethylene/ poly(ethylene oxide glycol terephtnalate]aviL a composition of 80/ 20 by weight, the poly(ethylene oxide) glycolunits having a molecular Weight of 6,000. Upon immersing the yarns in ahot 5% solution of NaOH the segments corresponding to 302, E04, inFIGURES 4, 5, and 6 9 are dissolved and residual cross-sections ofpoly(ethylene terephthalate) corresponding to ltll, 103, 105 in FIG-URES 4, 5, and 6 remain in the respective yarns.

EXAMPLE VII Using the apparatus and polymers of Example IV, thepositions of the two polymers were reversed. The polyester and polyamidewere extruded at 290 C. at a ratio of 12/16 by volume respectively andthe composite filaments wound up at 500 y.p.m. The yarn was drawn 4.2xover a 100 C. pin. A typical cross-section of the drawn filament isshown in FIGURE 9. A portion of a yarn was wrapped on a perforated metaltube and immersed in acetone for minutes. The dried yarn was pulled overthe edge of a glass microscope slide under a tension of about 0.5 g.p.d.so that the yarn suffered a 90 change of direction in the process. Theabove process caused the filament to partially fragment longitudinallyalong the interfaces of the sectors. A total of three passages of theyarn over the sharp edge caused complete separation of the polyester andpolyamide segments so that the yarn was composed of filaments which incross-section resembled 110 and 111 of FIGURE 9.

The compo-site filaments in the above drawn yarn were also completelyseparated into the polymeric components by one passage through an airjet as described in US. Patent No. 2,783,609 at a feed rate of 50y.p.rn. and a windup rate of 48 y.p.m. using two cu. ft. of air perminute at 90 psi. to operate the jet.

A portion of the above-drawn yarn not exposed to acetone or fragmentedwas wound on a perforated metal tube and placed in 98% formic acid atthe boiling point for 30 minutes. The tube and yarn was then placed incold formic acid for an additional minutes, rinsed with water and dried.The residual polyester filaments, which in cross-section resembledsegment 110 of FIGURE 9, had a tenacity of 3.6 g.p.d., an ultimateelongation of 31%, 21 Mi of 6-3, and a denier per filament of 1.0. Theyarn was used as a filling face in the weaving of a satin with yarn ofround cross-section, poly(ethylene terephthalate), as a warp. The fabrichad a dry, crisp, silk-like handle across the fillin band but was lesssilk-like than the fabric of Example I.

EXAMPLE VIII Using the apparatus and polymers as in Example VIIcomposite filaments are extruded and the continuous laments Wound up at500 y.p.m. The yarn is dipped in acetone and then drawn 2X over a pin at88 C. The segments of polyester break and split during drawing so that ayarn somewhat resembling a yarn spun from staple fibers is obtained inwhich the bundle of cruciform-like filaments of polyamide incross-section have the broken short lengths of polyester microfiberssubstantially evenly randomly interposed and engaged therewith whichproject laterally beyond the original periphery of the filaments.

EXAMPLE IX Solutions of polyacrylonitrile and cellulose acetate, both indimethylformamide are dry spun from the spinneret of Example IV. Theresulting filaments in cross section have alternate segments of the twopolymers with a crenulated periphery. An acetone bath dissolves thecellulose acetate portions of the filaments and leaves small denierfilaments of polyacrylonitrile of shape similar to FIGURE 8.

EXAMPLE X Linear polypropylene having a melt index of 9 andpoly(hexamethylene adipamide) having a relative viscosity of 39 wereextruded in equal proportions by weight following the general procedureof Example TI. The filaments were drawn to a ratio of 2.7, the drawnyarn consisting of 34 filaments having a denier of 2.53 each. Thefilaments were treated as in Example II except that the heat settingstep was omitted. The filaments which were round in cross-section weresplit by suitable mechanical action into elliptical polyamide filamentsand crescent shaped linear polypropylene filaments. The fabric made ofsuch separated component filaments had excellent bulk and cover and wassimilar to a fine cotton fabric in hand.

The composite filaments have been produced in the examples by the meltspinning technique. Obviously, other spinning methods like plasticizedmelt spinning, dry spinning, wet spinning, can be employed successfully.In some instances, particularly when the melting behavior or thesolubility of the components in a combination would not permit spinningthe components by similar methods, a combination of dissimilar methodscan be used. Thus, for instance, one component, can be spun as asolution in a high boiling solvent or as a plasticized melt, while theother component is extruded as a molten polymer. In these instances, thesolvents or plasticizers may be wholly or partially removedsubsequently, preferably by washing them out by the help of low boilingsolvents.

The composite filaments illustrated in many of the examples of thisinvention have substantially, smoothly rounded cross-sections beforeseparating of the components. Others have trilobal shapes. However, itwill be apparent to those in the art that by altering the shape of theorifice, the final cross-section can be controlled to a certain extent.Although square filaments cannot be extruded, filaments in cross-sectionwhich resemble a square with rounded corners can be obtained by the useof square or slotted orifices and these in turn would offer segmentsthat are plane triangles or a combination of plane and curvilineartriangles for example. Similarly, cross-sections in the shape ofellipses, cruciforms, etc., can be extruded and segments placed in suchfilaments as desired. Generally, by smoothly rounded cross sections, across section being free from sharp points and edges is intended.

It will also be obvious to those skilled in the art that othermodifications of the composite filaments and hence of the shape of theresidual filaments after dissolution can be altered by changing thenumber and placement of the upper orifices 32 (FIGURE 1). Other means ofaltering the configuration of the composite filaments will be by varyingthe diameters of the upper orifices used in relation to the size of theplateaus, and/ or the rate at which polymers are extruded through theupper orifices 32 and over the plateau. Alteration of the viscosities ofthe component polymers affects the configuration obtained. A lowviscosity polymer tends to be pushed inward more readily by the fiow ofa more viscous polymer and hence alters the shape of the segment that itwill make. The configuration in the component filaments is also affectedby the interfacial tension and the individual tendencies of the polymersto set the spinneret surfaces.

Although the spinneret used in the examples is a convenient apparatusfor the preparation of the filaments of this invention it will beobvious to those skilled in the art that other spinnerets can be used.Other spinnerets permit the production of filaments or ribbons havingalternating segments as shown in FIGURE 10 which can be split ordissolved apart to give sharp edged filaments.

The process of this invention affords a convenient means of obtainingfilaments having one or more sharp points in transverse cross-sectionand of a lower denier than can be otherwise attained. Thus, theinvention permits the production of sharp-edged filaments having adenier of 0.1 to 10 or larger. Its greatest utility, however, is in therange of 0.1 to 5 denier per filament. The novel filaments and yarns canbe used to obtain new and improved effects in fabric handle, scroop,appearance and covering power by proper selection of the polymercomposition and filamentary cross-section.

Suitable pairs of components for use in this invention can be found inall groups of synthetic fiber-forming materials. Where it is desired toseparate the filament into its component sections by mechanical action,the components should have low adhesion to each other. Obviously, thisis not necessary where one component of the pair is to be removed bydissolution or chemical decomposition. Because of their commercialavailability, ease of processing and excellent properties, thecondensation polymers and copolymers, e.g., polyamides, polysulfonamidesand polyesters and particularly those that can be readily melt spun arepreferred for application in this method. Suitable polymers can be foundfor instance among the fiber-forming polyamides and the polyesters whichare described in such patents as US. Patents 2,071,250; 2,071,253;2,130,523; 2,130,948; 2,190,770; and 2,465,319. The preferred group ofpolyamicles comprises poly(hexamethylene-adipamide) poly (hexamethylenesebacamide), poly(epsilon-caproamide) and the copolymers thereof.Suitable polyesters, besides poly (ethylene terephthalate), are thecorresponding copolymers containing sebacic acid, adipic acid,isophthalic acid as well as the polyesters containing recurring unitsderived from glycols with more than two carbons in the chain, e.g.,diethylene glycol, butylene glycol, decamethylene glycol andtrans-bis-1,4-(hydroxy methyD-cyclohexane.

Other groups of polymers useful as components in filaments of thepresent invention can be found among the polyurethanes, the polyureas,cellulose esters and cellulose ethers as well as among the polyvinylcompounds including such polymers as polyethylene, polyacrylonitrile,polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, andcopolymers containing the monomers of these polymers and similarpolymers as disclosed in US. Patents 2,601,256; 2,527,300; 2,456,360;and 2,436,926.

When it is desired to remove all sections composed of one polymercomposition by dissolution, a solvent for such polymer is selected thatwill not dissolve or have an adverse efiect on sections composed ofother polymer compositions. Thus, as illustrated in Example IX, formicacid may be used to remove the polyamide sections from the filamenthaving both polyester and polyamide sections in its cross-section. Theextent of dissolution of the soluble portion can be controlled asdesired.

Similarly, all sections composed of one polymer com position can beremoved by chemical decomposition. Thus, polyester sections of apolysegmented filament having alternate polyester and polyarnidesections, would be degraded by treatment with hot caustic as would thecopolyamide or polyurea portions of polysegmented filaments havingcopolyamide-polyacrylonitrile or polyureapolyacrylonitrile alternatingsections by treatment with mineral acids.

The preferred filaments for the production of improved silk-like yarnsof improved aesthetics and properties are the two component filaments inwhich the two components adhere sufiiciently during the spinning anddrawing of the yarn but may be later split into individual componentswhen the adhesive bond holding the filament components together isbroken or one of the components is'dissolved away. For this purpose thepolyamide-polyester combinations are most suitable. These filaments havethe advantage that the as-spun yarn is of sufliciently high denier sothat it is easily handled, while the benefits of much lower denier,finer filaments are realized in the final yarn due to the splitting orseparation of the filament component. In addition, differentialshrinkage provides bulk and cover in the yarn.

In producing silk-like yarns the denier of the lower shrinkage componentshould be lower than that of the higher shrinkage component and thedenier of the lower shrinkage components should preferably be no higherthan l.8. The denier of the higher shrinkage component preferably shouldbe higher than that of the lower shrinkage component in order to providethe desired resilience in the yarn. However, if both componentsbasically have high resilience this is not necessary. The shrinkage re-12 ferred to here is the shrinkage encountered in heat setting offabric.

The yarn of Example VIII is believed to have valuable uses in theproduction of improved fabrics having high bulk, cover, the scroop andhand of high quality fabrics.

The preferred filaments for making silk-like yarns have thecharacteristic that they crimp when subjected to boiling water and canbe split when subjected to suificient mechanical working. For producingyarns for this type, the polyester-polyamide combination is mostsuitable.

In order that the preferred composite filaments perform satisfactorilyduring spinning and drawing, and yet are substantially separated easilyby suitable mechanical action into individual components, the averageadhesion force between the dry filament components should preferably beat least 13 g./ cm. and obviously can be no higher than the force todraw the weaker material of the two components.

The difference in shrinkage between the different components of thefilament should be at least 1% in order to provide the necessary bulkand cover in fabrics. For the production of silk-like yarns, thediiferential shrinkage should be in the range of about 1 to 8%preferably 2 to 5%. As indicated above the difference in shrinkagerefers to the difference realized in the complete heat treatment of thefilaments, which may include a boiling water treatment and a heatsetting treatment.

In accordance with the requirements of the Patent Laws, I have describedvarious embodiments of my invention. Modifications and other embodimentsmay occur to those skilled in the art and such of these as fall withinthe spirit of my invention are intended to be covered by the followingclaims.

I claim:

1. A unitary spun composite filament having a substantially uniformlyshaped transverse cross-section along its length with a smoothly roundedcontour, said filament comprising a first longitudinally extendingcomponent of substantially uniformly shaped cross section along itslength of one synthetic polymeric composition, and an adhering seconddistinct longitudinally extending component of substantially constantcross section of another synthetic polymeric composition, saidcomponents closely fitted together along at least one contacting surfaceto form the composite filament, said contacting surface form ing atleast one longitudinally extending sharp-edge configuration, saidadherent components readily separable along said surface into separateindependent filaments at least one of which is provided with alongitudinally ex tending sharp-edge configuration.

2. The composite filament of claim 1 in which the component providedwith the sharp-edge configuration has a denier in the range of about 0.1and 5.0.

3. The composite filament of claim 2 in which one of said components isof a poly(ethylene terephthalate) composition and said other componentis of a poly(hexamethylene adipamide) composition.

4. The composite filament of claim 2 in which said component providedwith the sharp-edge configuration is of a polyacrylonitrile composition.

5. A unitary spun composite filament having a substantially uniformlyshaped cross section along its length with a smoothly rounded contour,said filament comprising a first longitudinally extending component ofsubstantially uniformly shaped cross section along its length of onesynthetic polymeric composition, said one composition being insoluble ina given solvent, and an adher ing second distinct longitudinallyextending component of substantially uniformly shaped cross sectionalong its length of another synthetic polymeric composition said anothercomposition being soluble in said given solvent, said components spuntogether and closely fitted along at least one longitudinally extendingcontacting surface to form the composite filament, said first componentcomprising a plurality of substantially parallel axially extendingportions in contact with each other along longitudinally extendinglines, said components spun together in fitting relationship along atleast one longitudinally extending contacting surface, said contactingsurface forming at least one longitudinally extending sharp-edgecoin-figuration, said components readily separable along said surfaceand said portions of said first component readily separable along saidlongitudinally extending lines to form a plural ity of filaments eachhaving at least one longitudinally extending sharp-edge.

6. The filament of claim in which said second component is readilyseparable from said first component by subjecting the composite filamentto the action of said given solvent.

7. The composite filament of claim 1 in which said one component is apoly(ethylene terephthalate) composition and said other component is apoly(epsilon caproamide) composition.

8. The composite filament of claim 1 in which one of said components isof a linear polyester composition and said other component is of alinear polyamide.

9. The composite filament of claim 1 in which one of said components isof a linear polyhydrocarbon composition and the said other component isof a linear polyamide composition.

10. The composite filament of claim 1 in which one of said components isof a linear polyester composition and said other component is of alinear polyhydrocarbon composition.

11. The composite filament of claim 1 in which the average level ofadhesion forces between said components is at least 13 g./cm. but lessthan the force required to draw either of said components.

12. The composite filament of claim 5 in which said component having thesharp-edge configuration has a denier of from about 0.1 to about 5.0.

13. A unitary spun composite filament having a substantially uniformlyshaped cross-section along its length with a smoothly rounded contour,said filament comprising a first longitudinally extending component ofone synthetic polymeric composition, and an adhering second distinctlongitudinally extending component of another synthetic polymericcomposition, said components closely fitted together along at least onecontacting surface to form the composite filament, said contactingsurface forming at least one longitudinally extending sharp-edgeconfiguration, said adherent components readily separable along saidsurface into separate independent filaments at least one of which isprovided with a longitudinally ex- 14 tending sharp-edge configuration,one of said components itself being additionally readily *fracturableand separable into a plurality of disconnected short lengths along itslength.

14. The composite filament of claim 13 in which said components thereofhave substantially uniformly shaped transverse cross sections alongtheir lengths.

15. A yarn comprising a uniformly randomly intermixed plurality offilaments, said plurality of intermixed filaments comprising a firstgroup of one synthetic polymeric composition and a second group of asecond synthetic polymeric composition, said filaments of said firstgroup of a continuous unbroken length throughout said yarn and having asubstantially constant irregular transverse cross section of a givensize, substantially all of said filaments of said second group brokeninto short lengths having a substantially constant sharp-pointedtransverse cross sections of a size significantly reduced relative tothe size of said cross section of said first group of filaments, thetransverse cross-sectional configurations of said filaments such that agiven predetermined number of each group can be fitted together in acomplementary geometric pattern to form a composite bundle pattern ofsubstantially rounded transverse cross-sectional form.

16. The yarn of claim 15 in which said filaments of said first group areof a linear polyamide composition and said filaments of said secondgroup are of a linear polyester composition.

17. The yarn of claim 15 in which said filaments of said second grouphave a denier of from about 0.1 to about 5.0.

18. The yarn of claim 15 in which said filaments of said second groupare adhered to said filaments of said first group over a first portionof their lengths and the second portion of said second group filamentsare separated from the other filaments and extend irregularly in adirection transversely of the other filament and yarn axes.

19. The filament of claim 1 wherein one of the said components is brokenat frequent intervals along the length thereof, the broken componentbeing separated from the unbroken component for a short distanceadjacent each break, the ends of the said separated, broken componentextending transversely of the unbroken com ponent to form fibrousprotrusions along the length of the filament.

References Cited in the file of this patent UNITED STATES PATENTS2,531,234 Seckel Nov. 2l, 1950

1. A UNITARY SPUN COMPOSITE FILAMENT HAVING A SUBSTANTIALLY UNIFORMLYSHAPED TRANSVERSE CROSS-SECTION ALONG ITS LENGTH WITH A SMOOTHLY ROUNDEDCONTOUR, SAID FILAMENT COMPRISING A FIRST LONGITUDINALLY EXTENDINGCOMPONENT OF SUBSTANTIALLY UNIFORMLY SHAPED CROSS SECTION ALONG ITSLENGTH OF ONE SYNTHETIC POLYMERIC COMPOSITION, AND AN ADHERING SECONDDISTINCT LONGITUDINALLY EXTENDING COMPONENT OF SUBSTANTIALLY CONSTANTCROSS SECTION OF ANOTHER SYNTHETIC POLYMERIC COMPOSITION, SAIDCOMPONENTS CLOSELY FITTED TOGETHER ALONG AT LEAST ONE CONTACTING SURFACETO FORM THE COMPOSITE FILAMENT, SAID CONTACTING SURFACE FORMING AT LEASTONE LONGITUDINALLY EXTENDING SHARP-EDGE CONFIGURATION, SAID ADHERENTCOMPONENTS READILY SEPARABLE ALONG SAID SURFACE INTO SEPARATEINDEPENDENT FILAMENTS AT LEAST ONE OF WHICH IS PROVIDED WITH ALONGITUDINALLY EXTENDING SHARP-EDGE CONFIGURATION.